Ditching Class A Amps due to Heat - Sort of a Poll

As it happens, Class A has been on my shopping list lately. So my answers are ’no’ to all three questions. But energy consumption issues do factor in.

As others have mentioned, various manufacturers use plateau bias to reduce typical class A power consumption, including Krell obviously (they’ve done that for a while). An Evolution 302 is probably the sweet spot for me (might stretch to the 400 mono pair, you never know). But it will have to be e-series, with the 2 watt standby, not the previous model, which uses ~60 watts just sitting idle. A pity, because there’s a very tidy and wicked looking black 302 (non-e) listed on the ’Gon right now.

The new one should use less energy that my current KAV-series Krell, which is AB but doesn’t have an efficient idle/standby. I'd be curious to see how a Purifi-based amp like the tidy units Mr March makes (I'm in Australia) would sound. But I'd need to hear one, last time I tried a modern design (LLC power supply, negative feedback) the sonics were disappointing.

We pay over the base market offer for 100% green power, but still factor energy efficiency into purchasing decisions. For most anything that uses significant power. There’s no need to be a f*ckwit.

@clearthinker

Sorr @axo1989 New Krells are NOT pure Class A. So called anticipator circuits don’t work So called plateau bias doesn’t work. No short cut to good sound. No free lunch.

I didn’t mention new Krell, Evolution series are D’Agostino designs (even though the e-series appeared after he and Rondi were forced out). And sustained plateau bias (and active cascoding) works—obviously—in the sense that it does what it’s designed to do, prevent notch distortion (the basic reason we want Class A) while reducing power consumption.

But if you want to argue that isn’t pure Class A, fair enough. I can change my answers to no, no and yes, respectively. Unless I change to high efficiency speakers and a low powered amp (and accept the tedium of constantly switching the damn thing off and on again) I’d steer clear of old-school Class A.

But while you're there, and since you are obviously into it, do you think the really old Krells sound better than the ones I have in mind?

PS: I did look longingly at the KAS pair that a guy in Melbourne advertises from time to time. Beautiful. Logistics though. Re your amps, KRS 200 was the original Class A version and the S was their sustained plateau bias model, yes?

@atmasphere thanks, that post was informative (both class D and Krell bias discussion). As I mentioned, I’d like to hear a Purifi class D design (either 1ET400 or 1ET7040 based).

I’m still happy to buy a Krell Evolution e-series though, I see it as the most technically advanced implementation of that design lineage. I can live with 2 watt standby. A (hypothetical) pair of 400 watt monos running 24/7 in old-school class A (no sliding bias) would be a madness though, as a main system left on all the time, consuming its rated power (multiplied by the efficiency factor) but achieving nothing when idle. That would be nothing for something.